Most biosensors in today's market and in research and development require a critical sample preparation procedure prior to analysis of cellular contents, such as nucleic acids and proteins. Ideally, sample preparation should minimize alterations to the sample (e.g., minimize chemical modification or mechanical damage to the sample), while also being easy to use, rapid, and cost-effective. Further, when the test sample is potentially hazardous, the biosensor should allow for containment and disposal of the sample after testing.
In particular, such sample preparation technologies should be compatible with point-of-care (POC) and nano/microfluidic devices. POC diagnostics offer great potential to detect and monitor infectious diseases at resource-limited settings because POC diagnostics can be taken to remote locations, decreasing the need for large decentralized diagnostic facilities (Lee W G et al., “Nano/microfluidics for diagnosis of infectious diseases in developing countries,” Adv. Drug Deliv. Rev. 2010 Mar. 18; 62(4-5):449-57). In addition, such POC and miniaturized fluidic devices can provide disposability, cost effectiveness, ease of use, and portability (Huckle D, “Point-of-care diagnostics: An advancing sector with nontechnical issues,” Expert Rev. Mol. Diagn. 2008 November; 8(6):679-88). Any proposed sample preparation technology should also be consistent with these desired POC characteristics.
One sample preparation step includes lysing of whole cell samples. Commercial acoustic lysing systems require large containers to hold fluids containing biological cells in proximity to an acoustic wave source. These containers are often tubes that only process large volumes and cannot be interfaced with nano/microfluidic POC devices, which generally process small sample volumes.
One particular challenge includes rapid and accurate detection of Mycobacterium tuberculosis (MTB) and drug-resistant forms thereof. MTB infects approximately one-third of the world's population. Eight million new cases of TB occur each year, accounting for approximately 7% of all deaths and 26% of all avoidable adult deaths in developing countries (De Cock K M et al., “Will DOTS do it? A reappraisal of tuberculosis control in countries with high rates of HIV infection,” Int. J. Tuberc. Lung Dis. 1999 June; 3(6):457-65). Multi drug-resistant (MDR) and extensively drug-resistant (XDR) strains have also relentlessly developed, reaching epidemic proportions in much of the developing world (Raviglione M C et al., “XDR tuberculosis—Implications for global public health,” N. Engl. J. Med. 2007 Feb. 15; 356(7):656-9).
A beneficial diagnostic system for MTB detection should be rapid, accurate, inexpensive, and clinically useful. Given the contagious nature of such MTB samples, POC devices and sample processing components are preferably disposable to protect the end-users from exposure to biohazardous waste. For on-site testing, the diagnostic system should have an integrated sample preparation component. The first step in sample preparation is to release MTB DNA for PCR identification, sequencing, and susceptibility profiling through mutation analysis. MTB provides several challenges as it is known to resist chemical and enzymatic lysing strategies and noted for its long-term (i.e., a few weeks) stability in a dry state, both of which challenge existing DNA extraction methods.
Therefore, a need remains for technology that releases cellular contents in a format compatible with miniaturized POC devices. In particular, there is a need for miniature acoustic lysing methods that can disrupt resilient cells (e.g., MTB) without the use of heat, chemicals, or enzymes that can interfere with PCR and DNA sequencing methods. Such systems and methods would also be beneficial if it minimized power consumption.